The aims of this study are to evaluate the interaction of temperament and dietary factors in early human development in order to determine their impact on weight gain. The increase in pediatric obesity is of great concern, as close to 6 million American children are fat enough to signal a significant public health problem. The health implications are serious, as diabetes, fatty liver and obstructive sleep apnea in children may foreshadow heart disease, or even cancer in in adulthood. In recent years, rates of overweight even among infants and young children have increased across all ethnicities, but especially minorities. While persistent overfeeding or low physical activity might seem to explain excessive early weight gain, studies of energy intake and expenditure in infancy have reported conflicting results. Because low-income, minority children who are formula-fed appear to be a population at particular risk for obesity, this study will enroll a sample of 100 low-income black and Hispanic mother-infant dyads (30 black and 70 Hispanic dyads), to track the infants over their first 5 years of development. Mothers will be recruited at WIC in the first few weeks after giving birth. Dyads will be visited in the families'homes when the infants are approximately 3, 6, and 12 months of age, and subsequently when they are 2, 3, 4, and 5 years old. Data collected will consist of demographic information, anthropometrical measures, maternal reports of infant/child eating patterns, maternal ratings of infant/child temperament, mechanical estimates of infant/child activity, ratings of maternal regulation of feeding, and measures of child development, self-esteem, and the home environment. The specific aims of the project are to assess maternal regulation of feeding in response to temperament, to determine how activity, difficulty, and sociability contribute to infant/child weight gain, and to evaluate the interactive impact of temperament factors, maternal behavior, and energy intake on excess childhood weight gain and other outcome measures.